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Ultraviolet (UV) water filtration is a purification process which uses artificially created ultraviolet light to kill biological contaminants such as pathogens and micro-organisms in a water supply. A popular method for disinfecting water, UV filtration is considered the safest and most reliable technique for eliminating micro-organisms like salmonella, coliform, and E. coli. Depending on need, UV water filtration units can treat a water supply as a whole or only that which is used.
During the purification process, water passes through rays emitted from a UV bulb enclosed in a translucent, protective cover. As the water moves through the flow chamber, it absorbs the UV rays. When the organisms in the water soak up the rays, their genetic material is altered, eliminating their ability to reproduce. Without the ability to reproduce, the organism is considered dead and its risk eliminated.
There are two terms commonly associated with UV water filtration systems: dosage and UVT. Dosage refers to the amount of ultraviolet energy needed to destroy contaminants and micro-organisms in the water. According to industry standard, a frequency of 254 nanometers is used to achieve disinfection. UVT, ultraviolet transmittance, is often used when discussing the amount of UV light needed to penetrate water flow.
The regulation of UV water filtration systems is determined and monitored by governmental organizations, such as the EPA and the Consumer Product and Safety Commission in the United States, and reputable, private sector laboratories. NSF International, a not-for-profit organization, is one of the most well-known laboratories to set the standards for home water treatment units. All UV filtration units are certified to meet NSF standard 55, which was specifically written for ultraviolet microbiological water treatment systems.
Two types of UV water filtration systems are commercially available. A point-of-entry system treats the water at its source, purifying the water before it reaches the tap. The other UV water filtration system, called point-of-use, is a filter that attaches to the faucet and purifies only water that is used.
Point-of-entry and point-of-use systems, both considered Class A filtration systems, are designed to remove micro-organisms and make water safe for consumption. Class B systems are a sub-set of point-of-use systems employed only for the supplemental use of removing additional contaminants following the initial disinfection conducted by a primary filtration system.
Ultraviolet systems do possess disadvantages. The systems are not sufficient enough to kill parasites such as Giardiasis duodenalis and Cryptosporidium, which both originate from biological contaminants like human and animal feces. UV filtration systems are not equipped with the capability to wash away sediments, namely iron. Unless a secondary filtration system is installed to siphon out sediment, frequent filter changes are required.